The present invention relates in general to telephony communications and more particularly to interfacing a computer with a modem for speakerphone voice communications.
Voice communications over the Public Switched Telephone Network (PSTN) are becoming an increasingly important aspect of computing. In particular, speakerphone operation has increasingly been offered as an optional feature of data modems. Such features allow the user to automatically dial or answer the telephone and speak to another person without the need for a telephone instrument and in a xe2x80x9chands-freexe2x80x9d manner. This operation is accomplished by employing a Digital Signal Processor (DSP) in the modem. The DSP manipulates local audio information, consisting of microphone input and speaker output, to perform echo cancellation and automatic gain control functions necessary for high-quality duplex speakerphone operation. In some models of the Compaq(copyright) Presario computers, for example, a voice coder-decoder (CODEC) in a modem is coupled directly to an external microphone and speaker by physical wires and plugs. This method, however, is inconvenient for portable computer applications because the external microphone and speaker add bulk and weight.
Many portable and notebook computers currently offered include internal sound systems which incorporate a microphone and a speaker which could, if properly interfaced, be used as the audio input and output for speakerphone operation. Co-pending U.S. application Ser. No. 08/496,537 titled xe2x80x9cComputer System Which Provides Analog Audio Communication Between a PC Card and the Computer""s Sound Systemxe2x80x9d filed Jun. 29, 1995, whose inventor is Leven E. Staples, and which is DATARACE, describes a modem with a CODEC directly connected to the microphone and speaker amplifier inside the computer in an analog fashion by multiplexing the use of pins in the computer-to-modem interface connector. This embodiment solves the portability problems, but requires a special implementation of the computer""s computer-to-modem interface which is not found in many commercial computer offerings.
Co-pending U.S. application Ser. No. 08/544,054 titled xe2x80x9cComputer System Which Provides Digital Audio Communication Between A PC Card and the Computer""s Sound Systemxe2x80x9d filed Oct. 17, 1995, whose inventor is Leven E. Staples, and which is assigned to DATARACE, describes a modem which multiplexes use of certain high address pins of a PCMCIA bus to transfer digital audio data from the modem to a CODEC in a sound card. This embodiment also solves the portability problems, but requires a non-standard use of the PCMCIA bus.
Therefore an interface for passing audio data between a portable computer""s internal sound system and a modem having duplex speakerphone capability which is compatible with existing electrical computer-to-modem interfaces is desired.
The present invention comprises a host computer system including one or more buses, a processor, modem and sound system configured to operate as a full duplex speakerphone. The sound system is coupled to a speaker and microphone of the computer. The modem is coupled to a telephone line which transfers audio signals via the PSTN between the subscriber using the computer as a speakerphone and a remote subscriber. The modem is configurable to operate in a speakerphone mode as will be described below. In addition, the modem may be configured in a normal mode, i.e., a data communications mode, to perform data communications, such as fax transmission or the transmission of Internet data, between the computer system and a data communications device on the telephone line.
The sound system receives a first analog audio input signal from the microphone and converts the first analog audio input signal into first digital audio output samples. The first digital audio output samples from the sound system are transferred to the modem, preferably by the host processor, a DMA controller, or through an intelligent bus master. The modem converts the first digital audio output samples into a first analog audio output signal for transmission on the telephone line. Conversely, the modem receives a second analog audio input signal from the telephone line and converts the second analog audio input signal into second digital audio samples. The second digital audio samples are transferred from the modem to the sound system. The sound system receives the second digital audio samples and converts the second digital audio samples into a second analog audio output signal for transmission to the speaker. Thus, the local subscriber utilizes the computer system as a speakerphone to perform audio communications with the remote subscriber.
In the preferred embodiment, the modem is comprised on a PC Card (formerly PCMCIA card) or CardBus card. In this embodiment, the computer system further comprises one or more PC Card slots, and the modem includes a PC Card interface portion for interfacing to the PC Card slots. This embodiment is particularly advantageous for use in notebook or portable computers which typically include PC Card slots. In an alternate embodiment, the modem is coupled to the processor via an expansion bus, such as an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, an SBus or a NuBus.
The modem includes an interface device which couples the modem to the processor via the PCMCIA bus or expansion bus. The modem further includes a coderdecoder (CODEC) coupled to the interface device. The interface device receives the first digital audio output samples and provides the first digital audio output samples to the CODEC. The CODEC receives the first digital audio output samples from the interface device and converts the first digital audio output samples into the first analog audio output signal for transmission on the telephone line. The CODEC receives the second analog audio input signal from the telephone line and converts the second analog audio input signal into the second digital audio samples. The interface device receives the second digital audio samples from the CODEC and provides the second digital audio samples to the bus.
The interface device includes a parallel to serial converter which receives the first digital audio samples from the bus in a parallel format, converts the first digital audio samples from a parallel format into a serial format, and provides the first digital audio samples to the CODEC in the serial format. The interface device further includes a serial to parallel converter which receives the second digital audio samples from the CODEC in a serial format, converts the second digital audio samples from a serial format into a parallel format, and provides the second digital audio samples to the bus in a parallel format. The interface device further includes interrupt logic for generating an interrupt to the processor or DMA controller upon completion of a transfer of one or more of the first digital audio samples from the parallel to serial converter to the CODEC and upon completion of a transfer of one or more of the second digital audio samples from the CODEC to the serial to parallel converter.
The modem further includes a digital signal processor (DSP) coupled between the CODEC and the interface device. The DSP transfers the first and second digital audio samples between the CODEC and the interface device. In addition, the DSP controls data communications between the computer system and a data communications device coupled to the telephone line. Preferably, the DSP and the interface device are coupled by a serial audio CODEC bus for transferring the first and second digital audio samples between the CODEC and the interface device in the serial format. The DSP and interface device are also coupled by a parallel data bus for transferring data associated with the data communications between the CODEC and the interface device. Preferably, the DSP performs echo cancellation and automatic gain control on the first and second digital audio samples as they are transferred between the CODEC and the interface device.